1. Field of the Invention
This invention relates to an optical disc driving technique for optically accessing an optical disc, and more particularly to a rate-variable optical disc recording method and apparatus that can vary a rate at which data is recorded onto the optical disc. Also this invention is directed to a rate-variable optical disc reproducing method and apparatus that can vary a rate at which data is reproduced from the optical disc.
2. Description of Prior Art
Generally, in order to record and reproduce an information on and from an optical disc accurately, a disc recording/reproducing apparatus must accurately recognize a position to be accessed and a driving condition in an optical disc. To this end, the optical disc is pre-formatted by a support information including a support synchronous signal for dividing a recording area, that is, track of the optical disc into a certain size of unit recording regions called "frames" or "sectors", hereinafter referred to as "frame" and a support address for indicating a position of each frame divided by the support synchronous signal. This support synchronous signal included in the support information serves to indicate a rotation velocity of the optical disc, that is, a playing speed of the track besides a function of dividing the track into frames. In other words, the support synchronous signal reports to the optical disc recording/reproducing apparatus a rate at which an information is recorded onto the optical disc as well as a rate at which an information is reproduced from the optical disc. Further, the support information may include a support clock for subdividing the recording unit regions. This support clock is a so-called "bi-phase clock" which is used to modulate a support synchronous signal, a support address and the like, and which is capable of indicating the rotating velocity of the optical disc more accurately compared with the support synchronous signal. In other words, the support clock can more accurately indicate a rate at which an information is recorded onto the optical disc and a rate at which an information is reproduced from the optical disc.
A disc recording/reproducing apparatus for recording and reproducing such an optical disc transfers an information to the optical disc at a constant rate and processes an information from the optical disc at a constant rate. In other words, a transfer rate of an information delivered between the disc recording/reproducing apparatus and the optical disc is fixed constantly. Accordingly, the disc recording/reproducing apparatus must drive a rotating velocity of the optical disc, that is, a playing speed of the track at a predetermined rate. To this end, the disc recording/reproducing apparatus performs the recording/reproducing operation of the information while monitoring if the optical disc, that is, the track is being rotated(or played) at a constant speed, based on a support information detected from the optical disc, that is, a support synchronous signal and/or a support clock. By means of such a disc recording/reproducing apparatus, an information is recorded or reproduced in a frame unit.
Meanwhile, various information, such as text data, audio data and video data, etc., is provided to a user of the disc recording/reproducing apparatus. Each of the various information is transferred at a very different transfer rate in accordance with the attribution and/or the composing system thereof. For example, the audio data is transferred at a very slow rate compared with the video data. Further, in the video data, analog broadcasting video data is transferred more slowly than digital broadcasting video data. Moreover, in the digital broadcasting video data, compressed image data is transferred more slowly than reference image data. A user utilizing various information different in the transfer rate as describe above desires that the various information should be recorded on the optical disc. Accordingly, the disc recording/reproducing apparatus requires a capability of recording various information in the transfer rate on the optical disc.
The disc recording/reproducing apparatus has to be able to accumulate an information from an information source temporarily in order to record on the optical disc various information having a transfer rate different from its own transfer rate. For example, in the case where an information more slow than the disc recording/reproducing apparatus in the transfer rate is inputted, the disc recording/reproducing apparatus must temporarily store the information until an information amount corresponding to the frame is inputted. Also, the disc driver must stop the recording operation until an information amount corresponding to the frame is accumulated. In other words, the recording operation in the disc driver must be periodically stopped. On the other hand, in the case where an information faster than the disc recording/reproducing apparatus in the transfer rate, the disc recording/reproducing apparatus must temporarily store an information exceeding an amount according to the frame. In this case, the disc recording/reproducing apparatus continues to perform after an input of the information is terminated in order to record the exceeding information.
As described above, in order to record a different rate of various information using the disc recording/reproducing apparatus, a buffer for temporarily storing the information is not only required, but also its recording operation is periodically stopped or be continued after an input of the information is terminated. In other words, the disc recording/reproducing apparatus can record an information having a transfer rate different from its own transfer rate on the optical disc in real time. The recording speed of the disc recording/reproducing apparatus, therefore, must be variable in accordance with a transfer rate of the information supplied to thereto.